Ellipticity measuring device

ABSTRACT

A balloon catheter is used for dilating tubular members of the body such as dilating stenotic aortic valve leaflets found in the aortic root, and measuring the shape and dimensions of the annulus. The balloon has two larger diameter bulbous regions; one is positioned in the left ventricular outflow tract (LVOT) and the other in the aortic sinus; a smaller diameter waist region is positioned across the aortic annulus. During inflation of the balloon, the balloon waist expands in diameter until it comes into contact with the aortic annulus. The balloon pressure and inflation volume is monitored during inflation so that an inflection point in the dP/dV curve is seen at the point of contact of the waist with the annulus. Radiopaque rings and/or marker bands in the device allow the size and orientation of the elliptical annulus to be calculated.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/598,085 filed Feb. 13, 2012 entitled Ellipticity MeasuringDevice, which is hereby incorporated herein by reference in itsentirety.

FIELD OF THE INVENTION

This invention is related to balloon catheters used for locating aposition within a blood vessel or tubular member of the body, dilatingtissue found within the tubular member, and measuring the diameter, theperimeter, or the elliptical index of the tissue or the tubular member.Specifically, this device is intended for locating the balloon acrossthe aortic annulus and aortic sinus, dilating the diseased aortic valveleaflets, and measuring the ellipticity, perimeter, or diametercharacteristics of the annulus or sinus region.

BACKGROUND

This patent application makes reference to and thereby incorporates allinformation found in U.S. patent application Ser. No. 10/856,494 (nowissued U.S. Pat. No. 7,618,432) and Ser. No. 10/846,613 (now issued U.S.Pat. No. 7,744,620) by Wesley Pedersen et al., particularly informationfound in the specification and drawings related to FIGS. 5A-5L. Also,this patent application makes reference to and thereby fullyincorporates all information found in issued U.S. Pat. No. 7,951,111 andU.S. patent application Ser. No. 13/108,938 by William J. Drasler et al.

Currently cylindrically shaped balloons are used to performvalvuloplasty procedures wherein the stenotic aortic valve leaflets aredilated or pushed back into the space of the aortic sinus. Thisprocedure is typically performed under fluoroscopic guidance while theheart is beating. Movement of the heart, flow of blood, and inaccuraciesin fluoroscopic guidance do not allow for accurate placement of thevalvuloplasty catheter across the aortic annulus and sinus.

Recently dogbone-shaped balloons have been presented (see U.S. patentapplication Ser. No. 10/856,494 by Wesley Pedersen) that provides forimproved positioning across the aortic annulus and sinus. Also,dogbone-shaped balloons have been presented that are able to measure thediameter of the aortic annulus as well as indicate the compliancecharacteristics of the aortic annulus (see William J. Drasler, U.S. Pat.No. 7,951,111).

Transcatheter aortic valve implantation (TAVI) is currently beingadopted as a method to treat stenotic aortic valve disease. In thisprocedure a stented aortic valve is placed across the aortic valveannulus and into the aortic sinus region to hold back the diseasednative valve leaflets. The stent portion of these valves tends to have around cross-sectional shape. The annulus, however, tends to have an ovalor elliptical shape owing to its anatomical location between thepulmonary valve and the mitral valve. Placement of a round stent intothe elliptical opening of the annulus tends to form a leak pathway forblood around the implanted valve at each end of the major axis of theelliptically shaped annulus.

In some instances the elliptical shape of the annulus is reformed into acircular shape with a specific diameter and perimeter as the TAVI deviceis implanted. For these patients whose annulus can be reformed, it isbeneficial to know the dimensions of the annulus in a stretchedcondition such that a properly sized TAVI device can be implantedwithout leakage of blood and without causing dissection of the annulus.For those patients that have a more calcified or less compliantelliptical annulus, it would be beneficial for the physician to knowunder what level of pressure the elliptical will reform to a roundshape, or alternately, if that patient is perhaps not a suitablecandidate for a TAVI device.

SUMMARY

The present invention is a balloon catheter used for dilating tubularmembers of the body such as dilating stenotic aortic valve leafletsfound in the aortic root, and measuring the shape and dimensions of theannulus. The balloon has two larger diameter bulbous regions; one ispositioned in the left ventricular outflow tract (LVOT) and the other inthe aortic sinus; a smaller diameter waist region is positioned acrossthe aortic annulus. During inflation of the balloon, the balloon waistexpands in diameter until it comes into contact with the aortic annulus.The balloon pressure and inflation volume is monitored during inflationso that an inflection point in the dP/dV curve is seen at the point ofcontact of the waist with the annulus.

Emb 1 Variable Waist and Variable Bulb Ring

A circular variable ring of radiopaque (ro) marker dots or deposits (forexample) located around the circumference of the balloon waist can beobserved under fluoroscopy to determine the perimeter of the annulus,its elliptical index (EI), and the appropriate size of TAVI device toimplant into the patient. The spacing between the ro marker dots can beset to a known dimension or a specified number of dots can be placedaround a perimeter of the balloon waist or bulb. The ro markersdescribed in this invention can alternately be ultrasound markers, MRImarkers, electromagnetic signal generators (such as small coils), orother means that are detectable via an energy means other thanfluoroscopy that is capable of penetrating its signal through humantissue.

An additional variable ring of ro markers can be placed around thedistal bulb of the balloon; the variable ring can change in its diameteror perimeter. Since this portion of the balloon is located in the LVOT,it will assume a circular cross-section when it is placed underpressure. The shape of the ring of bulb markers under fluoroscopy willbe determined by the angle, theta, of x-ray beam with respect to thez-axis of the catheter. For most fluoroscopic views the shape willassume that of an ellipse with theta equal to arc cos (major axis/minoraxis). The size of the viewed ellipse can be influenced by magnificationwhich is affected by the distance of the object of interest from theenergy source and from the collector means. With the angle, theta,known, one can then determine the elliptical index (i.e., ratio of majoraxis to minor axis) of the annulus. Thus, one can measure the ratio ofmajor to minor axes of the annulus ellipse and calculate the ellipticalindex, EI, of the annulus by examining a balloon having one portion withan RO ring that is known to be round and another portion with an RO ringin an area of interest and that can be used to measure its EI. This EIinformation can be determined from only a single fluoroscopic image.Although the size of the ellipse is influenced by a magnificationfactor, the EI measurements for the annulus via the bulb ring arerelatively accurate and not significantly influenced by magnification,as long as the bulb ring is within 1-4 cm of the waist ring.

Emb 2 Waist and Bulb Ring plus Shaft Markers

In an alternate embodiment one can measure the absolute dimension forthe waist by using linear ro markers placed along a linear span of theshaft beneath the balloon waist along the guidewire tubing. The angle,theta, is known from measurement of the ratio of the major and minoraxes of the bulb ro markers, minor axis/major axis=cos(theta). Thelength between marker bands can be used to determine the absolutedimensions and absolute shape of the annulus. The unmagnified length orspan for the linear span of ro markers is found from the angle theta as:unmagnified span=actual span(sin(theta)). The magnification factor isthen determined by Magnification factor=measured linear span/unmagnifiedlinear span.

Emb 3 Waist and Absolute Bulb Ring

In still another embodiment the ring of ro markers found on the distalbulb of the balloon is formed such that the diameter of the ring is afixed and known diameter. This can be accomplished via several of themanufacturing methods described in the prior art referenced in thisapplication. For example, a less compliant material can be placed aroundthe bulb region of the balloon. Upon examination of the shape of thecircular bulb markers under fluoroscopy, the length of the major axis ofthe image will be reflective of the actual diameter of the circularring. The minor axis will be equal to the major axis length multipliedby cos(theta). A fixed spacing between ro deposits around the balloonperimeter can assist in determining local dimensions of the waist orbulb.

The magnification effect that can occur when viewing an x-ray orfluoroscopic image is generally proportional to the distance between theobject being imaged and the collector device that receives the x-ray orother energy stream or means. Magnification of the fluoroscopic signalcan affect the length of a linear span of ro markers as viewed on itsfluoroscopic image; the use of a fixed ro ring of ro markers, however,is not affected by magnification affects since the major axis as viewedin the fluoroscopic image is a correct interpretation of the fixedcircular diameter of the ro ring. Generally, the location of the bulbring is close enough to the waist ring such that this difference doesnot produce a significant error in the magnification, (i.e., the erroris less than 1 mm).

Emb 4 2 Bulb Rings and a Waist Ring

In yet another embodiment the balloon can be formed with fixed ro markerrings around each of the bulbs and an expandable of variable ring aroundthe waist. The actual dimension for the waist and annulus would be anaverage of the dimensions as identified by an average of two absolutemeasurements of two RO rings that are located both closer to and fartherfrom the collector device by an equal amount. The centrally locatedwaist between the two bulb ro marker rings then allows the magnificationto be addressed by using an average dimension for the bulb ringdiameters as viewed on the fluoroscopy images.

Emb 5 Multiple Images with Waist Ring and Shaft Markers

In yet further another embodiment the balloon having a waist ring andshaft markers is located across the annulus. A fluoroscopic image istaken and the ratio of linear span as observed with respect to theactual linear span of the shaft markers. A second image is taken byrotating the image camera through an angle, phi, along a second axis forthe x-ray camera. The second fluoroscopic image will have a differentratio for the observed length/actual length for a linear span of romarkers. The fluoroscopic image will also be rotated in the image planeby an angle, beta. There is only one true location for the z-axis of thecatheter and the position of the object of interest, i.e., the fixed orvariable span of ro markers that allows a measurement of two differentlength ratios and two magnification factors after the camera has beenrotated a known number of degrees.

Once the shaft direction is known, and the magnification is known forthe object of interest, the camera can be positioned such that itprojects an image in any desired view. For example, the balloon can beobserved in a plane that is perpendicular to the shaft. Rotating thecamera around the shaft, around the z-axis, can provide multiple imagesof the annulus as viewed from around the catheter shaft. Such images canprovide relative or absolute dimensions of the major and minor axes ofthe elliptical annulus (via view of the waist ring) along with all otherimages located in between. Alternately, positioning the camera to viewdirectly down the z-axis of the catheter will allow visualization of thewaist ring directly with one view. A catheter with an absolute bulb ringdiameter would provide the absolute dimensions for the ellipticalannulus. A catheter with a variable bulb ring will provide relativedimensions of the elliptical annulus and can be used to identify anellipticity index, EI.

Additionally, the camera could be repositioned at an oblique angle withrespect to the axis with a specific known angle, theta, and with aspecifically known magnification. The major axis of the round fixed roring as seen on fluoroscopy can define an x-axis, and the length of themajor axis is equal to the diameter of the fixed ring ro span; thefluoroscopic view of the waist in a similar x-direction will have anaccurate dimension, using the fixed ro ring as a basis. The dimension ofthe image of the waist ring in a y-direction perpendicular to thex-direction will have dimensions that have been reduced by a factor ofcos(theta). The major and minor axes of the annulus ellipse can bedetermined by vector components in the x-axis and adjusted y-axiscomponents.

The balloon waist is formed from a semi-compliant (sc) material that isable to stretch under pressure until it comes into contact with theannulus as the balloon is being inflated. During inflation, the balloonpressure and inflation volume is monitored such that during contact ofthe waist with the aortic annulus an inflection point is observed in thedP/dV curve. At the point of contact fluoroscopy, ultrasound, RMI,electromagnetic signaling, or other means can be used to examine theimage and determine the shape of the annulus, its EI, and in someembodiments determine its absolute dimensions.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which

FIG. 1 is a top cross sectional view of an aortic annulus;

FIG. 2 is a cross sectional view of a balloon catheter within an aorticvalve according to the present invention;

FIG. 3 is a cross sectional side view of a balloon catheter according tothe present invention;

FIG. 4 is a cross sectional side view of a balloon catheter according tothe present invention;

FIG. 5 is a cross sectional side view of a balloon catheter according tothe present invention;

FIG. 6A is a cross sectional side view of a balloon catheter accordingto the present invention;

FIGS. 6B-6E are various coordinate systems relating to a ballooncatheter according to the present invention;

FIG. 7 illustrates calculation of a magnification factor relating to aballoon catheter according to the present invention;

FIGS. 8A-8D are various coordinate systems relating to a ballooncatheter according to the present invention;

FIG. 9A is a cross sectional side view of a balloon catheter accordingto the present invention; and,

FIG. 9B is a profile cross sectional side view of a balloon catheteraccording to the present invention.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

The present invention is a catheter with a balloon located at the distalportion for transcutaneous delivery into a tubular member of the bodyand more specifically it can be used during the TAVI procedure. A regionof the balloon provides information concerning the shape and size of thetubular member such as the annulus or the aortic sinus. Another regionof the balloon can be used to dilate diseased leaflets of the aorticvalve. The balloon can in some embodiments be used to identify arelative shape of the annulus and in other embodiments it can provideabsolute dimensions for the annulus or aortic sinus region.

The shape of the aortic annulus 5 is generally elliptical or oval in across-sectional view as shown in FIG. 1. The aortic annulus 5 is locatedbetween the pulmonary artery, PA, the mitral valve annulus, MV, and thetricuspid valve, TV. Generally, the major axis 10 extends along themitral valve portion of the aortic annulus 5. The minor axis 15 of theannulus 5 is directed perpendicular to the major axis 10. When a stentedvalve used for the TAVI procedure is implanted across the ellipticalannulus, it can form a perivalvular leak 20 these leaks tend to occur atthe ends of the major axis 10. Perivalvular leaks 20 are exacerbated bythe presence of calcium nodules.

A view of the annulus 5 and aortic sinus region 25 via a longitudinalsection is shown in FIG. 2. The aortic annulus 5 is shown as thenarrowest region after the diseased leaflets 65 have been pushed asideinto the aortic sinus region 25. The waist 30 of the balloon 32 of thepresent invention forms the narrowest region of the balloon and isintended to be positioned adjacent to the aortic annulus 5. The waist 30is intended to stretch outwardly under increasing balloon pressure toplace the waist into contact with the elliptically shaped annulus alongits entire perimeter. The distal bulb 35 forms another region of theballoon 32 that is positioned in the left ventricular outflow tract,LVOT 40. The proximal bulb 45 forms another balloon region that ispositioned in the aortic sinus 25. It is the proximal bulb 45 that isresponsible for dilating the diseased native leaflets 65 outwards intothe AS region.

As the balloon 32 is inflated, the distal bulb 35 is able to expandoutwardly without significant restriction from adjacent tissues andhence will assume a round cross-sectional shape. The material ofconstruction for the distal bulb region can be semi-compliant (sc) ornoncompliant (nc) polymeric material. The sc material option for thedistal bulb 35 does not have the larger compliance associated with thesc waist region 55. The distal bulb region 35 of the balloon 32 islarger in diameter than the waist diameter 55 and the aortic annulus 5and serves to hold the balloon 32 in position such that it cannot movetoward the aorta. The distal bulb 35 should have a larger perimeter thanthe perimeter of the annulus 5; for example the proximal bulb diameter60 of the proximal bulb should be 1-7 mm larger than the effectivediameter of the annulus 5 (the diameter of a circle with the sameperimeter as the annulus 5). The sc material for the distal bulb 35, forexample, can be nylon or other polymer that has substantially reachedits maximum diameter at a pressure of 3-4 atm. For a nc distal bulb 35,a PET, nylon, or fiber wrap can be used to reduce the amount ofcompliance found in the distal bulb 35. A nc distal bulb 35 shoulddilate or stretch in diameter less than 1-3% for a pressure of 1-4 atmto provide a known fixed diameter with 1 mm accuracy or better. A scdistal balloon region can expand approximately 3-6% for a pressureincrease from 1-4 atm. Other processing methods can be used as describedin the earlier referenced patents.

The proximal bulb 45 is similarly formed from sc or nc material asdescribed for the distal bulb. The proximal bulb 45 is also larger, wheninflated, than the waist 30 or annulus 5. The proximal bulb 45 serves todilate the leaflets 65 outwards as well as prevent the balloon 32 frommigrating under pressure back into the left ventricle. Contact of theproximal bulb 45 with the valve leaflets 65 occurs at low pressures of0-2 atm and generally pushes the leaflets back into the aortic sinusregion 25 upon reaching a pressure of 2 atm. The proximal bulb 45 issized to not allow the 25, including the volume of the diseased leaflets65, to dissect upon inflation to a pressure of up to 4 atm.

The waist 30 is formed from a sc material that is more compliant thaneither the distal bulb 35 or proximal bulb 45. The waist 30 should beable to expand up to 4-5 mm in diameter when the pressure increases fromapproximately 2 to 4 atm. It can be formed, for example of apolyurethane, nylon, or other sc material. The material for the waist 30can be an elastomeric material such as silicone or other cross-linkedpolymer. The waist 30 can be formed from the same material as the bulbsbut can be processed such that it is able to expand outwards from asmaller diameter to a larger diameter as the pressure is increased from0-4 atm; the diameter of the waist always being smaller than that of thebulbs, even at 4 atm. Under low pressures of approximately 0-2 atm thewaist 30 expands via an extension deformation but has not made contactwith the annulus 5. Thus the waist 30 is sized such that its perimeteror effective diameter (of a circle with the same perimeter as an oval)is smaller than the annulus perimeter at less than 2 atm. The waist 30must expand to reach and contact the annulus diameter that could be 4-5mm larger than its lower pressure diameter at approximately 2 atm orbelow.

As the waist 30 expands in diameter under increasing inflation pressureor inflation volume, the perimeter of the waist 30 comes into contactwith the perimeter of the annulus 5. At this contact point, aninflection is observed in the dP/dV curve for the balloon. Thisinflection point generally occurs at a pressure of approximately 2-3.5atm; the inflection occurs after the leaflets 65 have been pushed aside.At a balloon pressure of approximately 2 atm the waist 30 will have agenerally ridged circular cross section and will try to force theelliptical annulus 5 into a circular shape. At the contact point, theoutward force exerted by the waist 30 onto the annulus 5 is zero.Further balloon pressure can be applied to further induce the annulus 5to form a round shape by enlarging the waist 30 and forcing it into around shape at higher pressures. If the waist 30 of the balloon 32remains elliptical, it is one purpose of one embodiment of the presentinvention to identify the ellipticity index, EI, for the annulus; the EIis the ratio of the major axis 10 to minor axis 15 of the ellipse. Inanother embodiment, the present invention will provide informationregarding the pressure required to form the elliptically shaped annulus5 into a circular shape. In another embodiment, the dimensions of theannulus 5 will be absolutely measured and reported to the operator toallow proper selection of the appropriate size of TAVI device toimplant.

In one embodiment, as shown in FIG. 2, the catheter 99 of the presentinvention is injected with a contrast medium that can be visualizedunder fluoroscopy. The fluoroscopy camera, FC, can be oriented such thatit directs x-rays in a direction perpendicular (i.e., theta=90 deg) tothe axis 70 of the catheter 99. This perpendicular orientation can beaccomplished by monitoring the fixed linear span 75 between two markerbands 80 located within the balloon 32 along the guidewire tubing 85 attwo or more oblique orientations (with respect to the catheter axis) ofthe camera around the perimeter of the balloon. Also, the diameter ofthe linear span as observed in the fluoroscopy plane will be measured.Geometrical considerations regarding the length of the fixed span withrespect to the camera orientation and rotation of the image of thelinear span (as well as its altered displacement) allow a determinationof the catheter axis 70 orientation and position of the object ofinterest (i.e., the linear span of ro markers or the aortic annulus, forexample) to be known in 3D space. Only one axis location in 3D spacewill be consistent with the two lengths of the fixed span and itsrotation in the fluoroscopic image plane at two different orientationsof the camera with respect to the catheter axis. Once the axisorientation is known, along with the position of the object of interest,the camera can then be placed, for example, perpendicular to thiscatheter axis, or at another angle. Rotating the camera, for example,around the catheter axis by 180 degrees, while observing the diameter ofthe waist under fluoroscopy at several (perhaps 2-8 distinct positions)camera orientations, will allow a determination of the ellipticityindex, EI, of the annulus to be observed, measured, and identified.Alternately, the camera can be placed to view along the z-axis 70 of thecatheter 99 or at any oblique angle with respect to the z-axis 70 of thecatheter 99.

FIG. 3 shows an embodiment of the present invention having a balloon 32with distal bulb 35, a proximal bulb 45, and a waist region 30. In oneembodiment, the balloon 32 has a circular waist variable ring 90 ofradiopaque (ro) deposits 95 placed around the waist 30; the variablewaist ring 90 is able to stretch or vary its perimeter since thedeposits are not continuous but are instead discrete deposits separatedby a space between individual ro deposits. The space between individualdeposits can be controlled if desired such that the spacing can be usedto contribute as a basis for determining the absolute dimensions of awaist ring or annulus. The ro deposits can be formed from tungsten orother ro material used in the art for ro markers, and can be applied tothe outside of the balloon via a liquid dispersion such as an ink or asa stamping process. The ro deposit 95 can be covered by a secondarycoating step to ensure that the ro deposit does not embolize.Alternately, the ro deposits can be applied via any other suitableprocess including plasma deposition, or trapping ro deposit materialbetween two layers of polymer such as two layers of balloon material.The proximal bulb or the balloon is located nearest to the manifold 97of the catheter 99.

In addition to the variable ring 90 located in the waist, one embodimenthas an additional ring 100 of ro deposits located around a circumferenceof the distal bulb 35. The ring 100 can be a variable ring as shown inFIG. 3 or it can be a fixed ring or a fixed span (i.e., having a fixeddiameter, perimeter, or span) as shown in later figures and embodiments.The distal bulb 35 is not restricted by surrounding tissue and canexpand freely under pressure. The variable ring located in the distalbulb region thereby forms a round shape when the balloon 32 is inflatedto a pressure of 1-4 atm. Observation under fluoroscopy of the minoraxis (i.e., the smaller viewed axis) of the round variable ring 100 willaccurately identify the plane that contains the fluoroscopy cameradirection and the z-axis 70 of the catheter 99. Observation andmeasurement of the major axis of the round variable ring 90 providesboth a direct measurement of the angle 105, theta, between thefluoroscopy camera and the z-axis 70 of the catheter, where theta=arccos (minor axis/major axis). Once the angle 105, theta, between thecamera FC and the catheter axis 70 is known, the ellipticity index, EI,for the annulus can then be determined. The length the ellipse asidentified by the variable waist ring 90 in the direction of the majoraxis of the distal bulb ring major axis is absolute and can be measureddirectly using the major axis of the distal bulb ring as a basis. Thelength of the ellipse in the direction of the minor axis of the distalbulb ring minor axis is measured directly using the minor axis of thedistal bulb ring as a basis (the minor axis of the ellipse can bemeasured directly and corrected by a factor of 1/cos(theta) and thenusing the distal bulb major axis as a basis). Each element of theannular ellipse can similarly be determined by breaking down its vectorsinto one that is parallel with the major axis of the distal bulb ringand parallel with the minor axis of the distal bulb ring 35. Hence, themajor and minor axis of the annular ellipse can be determined by usingthe distal bulb ring for establishing a coordinate system within thecross-section of the balloon and using the distal bulb as a basis fordetermining relative dimensions for the major and minor axes for theannular ellipse. The ellipticity index, EI, can then be calculated forthe annulus, where EI=major axis/minor axis.

Variable Waist Ring and Fixed Bulb Ring:

In yet another embodiment shown in FIG. 4 the distal bulb 35 can have afixed bulb ring 110 of ro markers 95 or a fixed span 75 of markers thathave a fixed and known diameter or perimeter. In this embodiment thedistal bulb 35 is formed from a nc material. As shown in FIG. 4, anouter wrap 115 can be place around the distal bulb 35 of an innerballoon 120 to form a nc distal bulb. The fixed bulb ring 110 can beplaced between two layers, for example, between the outer wrap 125 andthe inner balloon 120 to ensure that the ro deposits 95 cannot embolize.An outer coating of polymeric material 125 can be applied to the outsideof the entire balloon 32, if desired, to coat over the ro deposits 95 toensure that they do not embolize; a flexible polyurethane coating ofless than 0.001 inch, for example, could be applied for this purpose.

This balloon 32 with a variable waist ring 90 and fixed bulb ring 110functions in a similar manner to the embodiment with the variable distalbulb ring. The distal bulb ring in this embodiment will expand underpressure to form a round shape with a known diameter. Measurement of themajor axis of the distal bulb ring under fluoroscopy will provide anexact basis from which to compare the measurements made in the annularellipse. The minor axis of the distal bulb under fluoroscopy can providea basis for measuring the annulus (i.e., the waist fixed ring) in adirection parallel with the minor axis of the distal bulb. With thisembodiment, the specific accurate dimensioning of the annulus can bedetermined with a single fluoroscopic image from an oblique orientationof the x-ray camera FC with respect to the z-axis 70 of the catheter 99.Other elements of the balloon bear reference numerals similar to thosedescribed in other embodiments.

Variable Bulb Ring and Linear Fixed Span:

In another embodiment the distal portion 35 of the catheter 99 has aguidewire tubing 85 that extends through the balloon 32. In addition tothe variable ring located in the waist 30, marker bands 80 can be placedalong the guidewire tubing 85 to form a fixed linear span of ro markers;the markers 80 are fixed at a specific and known distance or span. Thedistance between two fixed span markers 80 is a function of the ratio ofthe observed linear span to the actual length of the linear span. Asdescribed earlier, two fluoroscopic images taken of the catheter willprovide a different effective length or span between the fixed spanmarkers 80. The two fluoroscopic images will also allow the angle ofrotation of the fluoroscopic image as well as its position to change.Information from the two fluoroscopic images are used to determine thelocation of the z-axis 70 in 3D space as well as the location of theobject of interest (i.e., this is equivalent to knowing themagnification for each of the positions). Only one position of thez-axis 70 in 3D space can exist that satisfies the two observations forthe two camera orientations. The magnification factor of the image isproportional to: (the distance from the x-ray emitter to thecollector)/distance from emitter to object of interest).

Once the z-axis 70 and the position of the object of interest has beenlocated in 3D space, images of the waist variable ring or ro ring can betaken from a known camera angle with respect to the z-axis 70. Theellipticity of the variable waist ring can then be determined using thefixed linear span of ro markers 80 along the guidewire tubing as abasis, where sin(theta)=(observed linear span/actual linearspan)(magnification factor). The plane that contains the x-rayprojection and the z-axis 70 will define the y-axis of the coordinatesystem that is perpendicular to the z-axis; the x-axis beingperpendicular to both the x and z axes. The dimensions of the annulusellipse in the x-axis is measured directly and uses the fixed linearspan corrected by the magnification factor and the y-axis is measureddirectly and adjusted by factor (1/cos(theta)) (magnification factor)and uses the fixed linear span as a basis.

Waist Ring and Two Bulb Rings:

In still another embodiment, as shown in FIGS. 3 and 4, the proximalbulb 45 can have a variable ro ring 100 or fixed ro ring 110. Thepresence of a ro ring on both the proximal bulb 45 and distal bulb 35allows the magnification factor associated with the distance between thedistal bulb 35 or proximal bulb 45 and the waist 30 to be taken intoconsideration. Since the waist 30 is located between the proximal bulb45 and distal bulb 35, the amount of magnification of the bulb withrespect to the waist 30 will be larger for one bulb and smaller for theother bulb, thereby allowing an average fixed ro span to be used tocalculate absolute dimensions for the annulus ellipse.

In another embodiment shown in FIG. 5 the balloon does not have abulbous shape but instead it has a cylindrical shape. In thisembodiment, a proximal balloon region 45 of the balloon 32 issemi-compliant and has a ro proximal variable ring 90. This ring 90would be placed adjacent to the annulus. More than one such variablerings 90 can be placed along the proximal sc region 45 of the balloon 32if necessary to enhance the likelihood that one of the rings 90 islocated adjacent to the annulus. A distal balloon region 35 can be sc ornc and has a ro distal ring 130. This ro ring 130 would be placed intothe LVOT where enough space exists to allow this region 35 of theballoon 32 to form a circular cross-sectional shape. The ro distal ring130 can be a variable or fixed ro ring. As described earlier, if the rodistal ring 130 is variable in diameter and perimeter, then only arelative dimensioning of the annulus can be obtained in determining theEI. If the distal ro ring 130 is a fixed ring, then absolute dimensionsfor the annulus ellipse can be obtained. The construction of the distalregion can be accomplished via placement of an outer wrap or an outercoating as described for earlier embodiments.

To better understand the capability of the present invention the bulbousballoon 32 is shown in FIGS. 6A-6E along with sketches showing theobserved images at an angle 105, theta, with respect to the z-axis 70.FIG. 6A shows the balloon having a round distal bulb ring having a fixedbulb ro ring with radius, R. The waist 30 has a waist variable ring 90of unknown diameter and shape. A fixed linear span of marker bands 80 islocated on the guidewire tubing and having a span of Zo units. An x-raycamera, source camera, or fluoroscopy camera, FC, positioned at an angle105, theta, with respect to the z-axis 70 directs its x-rays toward theballoon 32.

A coordinate system 135 with x and y axes drawn through the fixed distalbulb is shown in FIG. 6B with the center of the circle, C, at thejunction of the x and y axes. The x and y coordinate system is drawnthrough an example actual elliptical waist ring 135 of ro markers inFIG. 6C. The observed shape on fluoroscopy for the fixed bulb ring inthe distal bulb is an ellipse 140 as shown in FIG. 6D. The observedshape on fluoroscopy for the example elliptical annulus is an alteredellipse 145 shown in FIG. 6E. The purpose of this exercise is to be ableto reconstruct the actual elliptical shape for the annulus based uponthe observed shape found for the actually round bulb distal ring 130.

From observation of FIGS. 6A, 6B, and 6D, the effective length for theminor axis, r, of the ellipse observed on fluoroscopy is R cos(theta),where r=R cos(theta). Therefore, by measuring the ratio of r/R one isable to determine theta. The magnitude of the length of the major axis,R, is not affected by the angle 105, theta, and therefore can be used asa basis for determining absolute length for the case of the fixed ringof ro markers. Magnification is not a concern when using a circle orring of fixed ro markers as long as the waist ring 90 is within a fewcentimeters of the bulb distal ring 130.

The observed image seen on fluoroscopy for the variable ring 90 found inthe waist 30 will be similarly reduced in magnitude in the y-axis by afactor of cos(theta). The x-axis for the fluoroscopic elliptical imageof the waist ring (or annulus) as identified in FIG. 6E lies in exactlythe same plane and is parallel to the major axis of the ellipse formedby the fluoroscopic image of the distal bulb ring 150 in FIG. 6D.

Any component in the x-axis of the observed image in FIG. 6E is anaccurate dimension and can be identified using the known basis dimensionof the x-axis dimension that is a representation of the circle found inthe distal bulb having the fixed diameter ro markers. The component ofthe observed ellipse in the x-direction, mjx, is the same as thex-component of the actual waist ellipse formed by the waist ring, MJx.Similarly, the component of any point found in the y-axis in theelliptical fluoroscopic image of waist ring 155 of FIG. 6E would bemultiplied by a factor (1/cos(theta)) to identify its actual accuratedimension as compared to the known basis dimension found in the distalbulb circle. The component of the observed ellipse in the y-direction,mjy, should be multiplied by a factor 1/cos(theta) to provide thex-component of the actual dimension of the waist ellipse in thex-direction, MJy. The magnitude of the major axis of the actual ellipseformed by the waist ring 155 is a vector sum of MJx and MJy.

FIG. 7 is intended to describe the magnification factor and theconsequences of this additional effect on the accuracy of dimensionaland shape analysis. The x-ray camera, source, or fluoroscopic camera,FC, is located at point S. The x-rays tend to fan out as they extendaway from the source. In this example the x-rays strike the object ofinterest (i.e., the ro markers) having a length of Zo and located adistance, S0, away. The collector plate (CP) or image intensifier islocated at a distance S1 from the source and received an image signalwith a magnified size of Z1. The image that is viewed by fluoroscopy andother means, such as ultrasound, would then be magnified such thatZ1=((S1)(Zo)/So).

The balloon waist and each of the bulbs are located within 2-4 cm ofeach other such that any magnification error associated with using anabsolute bulb dimension to determining an annulus dimension will not belarge, i.e., less than 1 mm. If one were to use the linear span 75 of romarkers along the guidewire tubing one would have to determine both theangle 150 of the x-ray source with respect to the z-axis 70 as well asthe magnification factor associated with its location from the source.To do this will require, as stated earlier, an additional fluoroscopicscan at, for example, two different camera positions or two differentdistances of the source, S, to the object to establish the location ofthe object of interest or to establish the magnification and to placethe z-axis 70 of the catheter 99 and the object of interest into a knownlocation in 3D space.

FIGS. 8A-8D are concept drawings that shows the fixed linear span of romarkers with a span of Zo located along the z-axis 70 of the catheter ofthe present invention. In an example shown in FIG. 8A the x-ray sourceis directing a stream of x-rays at an angle, theta1, with respect to thecatheter axis 70. The x-rays can be directed from anywhere along asurface, for example, of a half sphere, HS, toward the object ofinterest, the fixed linear span of ro markers or marker bands. Thesource camera or fluoroscopic camera, FC, can be rotated along a cameraaxis, (i.e., c-axis 160) with an angle, phi, in the circumferentialdirection, and the camera is rotated with an arm length, AL, forrotating around the c-axis. The angle of the camera, phi, with respectto its starting position will be arbitrarily set to phi1. As mentionedearlier, the length of the observed linear span via fluoroscopy would beZo sin(theta1), as shown in FIG. 8B, if the magnification factor wasunity. Thus, theta1 is known for a unity magnification. In FIG. 8B, they-axis for the catheter has been set to align, for example with thedirection of the observed image of the linear span.

To adequately consider the true magnification (as described in FIG. 8),a second fluoroscopy image is taken by rotating, for example, the cameraalong its c-axis to a new camera angle of phi2 as shown in FIG. 8C. Thex-rays enter the half sphere, HS, at some location that is oblique tothe x-, y-, and z-axes. The observed fluoroscopic image of the length ofthe fixed linear span can be measured as Zo sin(theta2), for amagnification of unity, as shown in FIG. 8D and will be displaced byrotation angle 165, beta, from the y-axis; the y-axis being set by thedirection of the first fluoroscopic image as seen in FIG. 8B.

Measurement of the effective length of the linear span of ro markers bymovement of an x-ray camera to two different locations allows a solutionto two equations with two unknowns. The two equations describing thelength of the linear span with respect to the angle of the x-ray ontothe z-axis of the catheter and the length of the linear span withrespect to its distance from the source and collector (as described bymagnification). The information that is measured and known variablesinclude the effective length of the linear span for each of thefluoroscopic images, the rotation angle and absolute position of thecamera for the first and second fluoroscopic images, and the rotationangle 165, beta, of the linear fluoroscopic image from the first tosecond fluoroscopic images, and the displacement of the fluoroscopicimage from its initial position or tissue entity, 170, located in afixed position within the patient. Such tissue entity can be a calcifiedaortic valve leaflet or other observable tissue member of the body.

The resulting determination of both the angle of the catheter shaft andthe position of the object of interest (or its magnification) in 3Dspace then allows the fluoroscopy camera, FC, to be placed into aposition such that a fluoroscopic view is made either perpendicular tothe z-axis of the catheter shaft 172 such as shown in FIG. 9A or in linewith the z-axis as shown in FIG. 9B, or at some oblique angle. Theperpendicular view allows measurement of the annulus from a longitudinalview of the balloon waist ring 175, with correction for magnification(for absolute dimensions), and this could be performed in several viewsaround the z-axis of the catheter. Also seen are the proximal bulb ring180 and distal ring 130. The end view as shown in FIG. 9B allows asingle view of the elliptical waist ring (or annulus) with a directreading of the EI from a single view from this direction. Absolutedimensions of the annulus can be determined from consideration of themagnification factor as determined via two prior fluoroscopic imagesthat would place the location of the fixed or variable ro markers in 3Dspace. Any other oblique view can be taken with the fluoroscopic camerawith the knowledge of the location of the z-axis, the location of the romarkers in 3D space, and the location of x-ray camera in 3D space.

It is understood that a patient or organ may move from one fluoroscopicimage to the next image. This movement can affect the accuracy ofrelative or absolute measurements related to dimensions of the annulusor shape of the annulus, including determination of EI. It is thereforeunderstood that identification of a physical entity located within thepatient's body can be identified such that the catheter position withrespect to this physical entity is monitored and measured during thefluoroscopic procedure. During at least two of the fluoroscopic images,the position of a fixed ro marker, for example, would be located and thedistance and angle of position of the ro markers from the physicalentity would be measured in a manner similar to that described for themeasurement of the linear fixed span of ro markers. Correction can bemade for movement of the patient with respect to the fluoroscopy camera,FC, as long as the catheter retains its position with respect to thephysical entity. Such physical entity for the case of TAVI procedurescould be a calcified valve leaflet or other calcium deposit, forexample.

The invention claimed is:
 1. A catheter for determining the size andshape of a tubular member of the body, said catheter comprising: aballoon having a first semi-compliant region and a second region, saidfirst semi-compliant region having a first span of radiopaque markerscomprising a variable ring of radiopaque markers, said second regionhaving a second span of radiopaque markers expanding to a predeterminedsize; said second region having a larger diameter than said first regionduring inflation of said balloon.
 2. The catheter of claim 1 whereinsaid second span of radiopaque markers remain a fixed distance away fromeach other on said second region.
 3. The catheter of claim 1 whereinsaid second region is a noncompliant region in which said second span ofradiopaque markers are positioned along a circumference of said secondregion of said balloon.
 4. The catheter of claim 1 wherein said balloonfurther comprising a third region, said first semi-compliant regionbeing positioned axially between said second and said third regions,said second region and said third region being larger in diameter thansaid first region during balloon inflation.
 5. The catheter of claim 4wherein said third region has a third span of radiopaque markers forminga ring.
 6. A catheter for determining the size and shape of a tubularmember of the body, said catheter comprising: a balloon having a firstregion comprising semi-compliant material and a second region comprisingnon-compliant material; said first region located adjacent to saidsecond region; a first ring of radiopaque markers located around saidfirst region; said first ring of radiopaque markers comprising a firstplurality of radiopaque markers that increase in distance from eachother along said first region during inflation of said balloon; a secondring of radiopaque markers located around said second region; saidsecond ring of radiopaque markers comprising a second plurality ofradiopaque markers that remain a constant distance from each other alongsaid second region during inflation; wherein said second ring ofradiopaque markers forms a known diameter when fully inflated.